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Human body louse is known to infest homeless people, jail inmates, alcoholics, people in refugee camps, institutional inhabitants, and historically, the troupes during the World Wars.[1] Louse infestation (pediculosis) is very contagious and is transmitted by close contact with humans and infested linen and clothes. In addition to the body louse, head and pubic louse also infest humans. Of the three types of lice, only body louse is known to transmit infections in humans.[2]
It requires conditions of poor hygiene and crowding for the body louse to cause infectious epidemics and outbreaks. Given the suitable conditions such as cold weather, crowding, and poor hygiene in the trenches, the louse-borne infections were reported in millions of troupes during the World Wars.[1] Body louse needs 4–5 blood meals per day and can bite 4–5 humans in crowded conditions in a day. Human body louse can transmit Bartonella quintana (bacterium), Borrelia recurrentis (spirochete), and Rickettsia prowazekii (rickettsia) infections to humans. Transmission of infectious agents can occur by contamination of conjunctiva, mucus membranes, or bite sites with either the feces or the body contents of crushed lice.[2]
During the World War 1, over 1 million troupes were infected with a bacterium B. quintana, originally called Rochalimaea quintana or Rickettsia quintana.[1] This organism caused a relapsing febrile illness with severe body aches, headache, maculopapular rash, conjunctivitis, and lymphadenopathy. The illness was termed as “Trench fever” because it was acquired while troupes were stationed for prolonged periods in the trenches.[3] Trench fever almost never results in mortality; however, it is associated with severe body aches and characteristic shin pain in the patients. On the other hand, the other two louse-borne infections relapsing fever and epidemic typhus have very high mortality in the untreated patients [Table 1]. The epidemic typhus caused by R. prowazekii and louse-borne relapsing fever caused by B. recurrentis have caused millions of deaths historically during wars, famines, disasters, and conditions of poverty.[2][Table 1] shows differentiating features of three main louse-borne infections in humans.
The louse-borne infections had become a rarity after the World Wars due to the advent of antibiotics and improvement in hygiene and because no major outbreaks were reported. In recent times, however, there are many reports of re-emergence of these infections, especially in the parts of the world affected by civil wars, conflicts, disasters, and famines, resulting in mass displacements of people who are forced to live in refugee camps under unhygienic conditions.[3] During the civil wars of Burundi, Rwanda, and Zairein in the 1990s, the rate of louse infestation among refugees reached 90%–100%.[2]
Modern-day physicians are mostly unaware of these infections; therefore, it is wiser to revisit their main characteristics and differentiating features [Table 1]. Presence of jaundice is a pointer toward B. recurrentis infection; however, endocarditis and bacillary angiomatosis are seen in B. quintana infection.[2]
All three louse-borne infections respond to treatment with doxycycline. In patients with chronic bacteremia with B. quintana, the recommended treatment is injection gentamicin for 14 days with oral doxycycline for 28 days.[2] For patients of Bartonella endocarditis, doxycycline treatment is extended for 42 days.[2]
To conclude, louse-borne infections are re-emerging in many parts of the world, especially those areas that are facing refugee situations, conflicts, famines, poverty, and disasters. Physicians need to be aware of the possibility of these infections in the susceptible populations. Louse-borne infections can have high mortality if untreated; however, timely treatment with doxycycline is lifesaving.
References 
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jgid.jgid_98_22
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